It sure would be a shame if the reason that number 4 piston goes is because of an oil issue and running richer will just wash gas down the cylinder walls and further starve the rings and lands of oil. You guys better be 100% sure that its a fueling issue before doing this.

My 2 pennies.

 

i think if that were the issue we would be seeing stock motors blow would we not?
since stock and stage 2 tunes are already just as rich as is being suggested here?

 

I'm being told by guys much smarter than me that lands usually blow out from oil problems. If its an A/F problem the top of the piston would be melted first.

All I'm saying is you might wanna put an EGT probe on on the car at least before you go adjusting A/F blindly.

 

I dont think anyone with jus stg 2 has blown up yet.

 

yeah I'm pretty sure when GM said that they would warranty the stage 2 they decided to make a safe tune to save them money from replacing engines. I guess they aren't as stupid as a lot of you guys thought about the tune lol.

 

I understand that. and I agree.

but my point was....stock and stage 2 are running this rich.
hes suggesting that people who are tuning themselves should ALSO be running that rich.

and as stated above....we havent had any stock/stage2 cars blow....so that would suggest that the AF of the stock/stage2 tunes isnt an issue.


Im no pro at this. im just deduction.

 

But...

We all know oil starvation will eat parts. Also a well known fact is detonation will pound a piston to pieces. We have cast pistons which will no way handle detonation for a long. How long? I don't know. Ring lands take a huge beating since the rings are holding back compression and exerting their force against the ring lands which appear to be the failure rather than a holed piston top.

On these motors that have broken ring lands, has the tuner gone extreme with ignition advance without running the appropriete amount of fuel to suppress detonation? Even at stock ignition advance, having not enough fuel in there will cause it to detonate which will eventually beat a piston to pieces. Also taking a beating will be the rod bearing. Has anyone checked the rod bearing clearance before & after a broken piston?

I am no expert by no means but I am not stupid either

Mike

 

There are other factors rather than A/F between the two tunes. PE on a stage 2 is actually set at lean best torque. The adders that richen don't come usually don't come into play until the car has been in power enrichment for an extended time.

Also the amount of cylinder pressure and heat generated with pulley of that size is significantly lower than most people that are melting engines.

I have no idea myself why piston 4 seems to be a problem, but this isn't exactly the first car I've modified the EFI (tuned). In my experience, going richer than rich best torque with any engine wil result in big problems down the road. When you get into the 10 range with air/fuel you will wash cylinder walls and you will do damage to rings and sleeves and contaminate the oil with gasoline.

Remember, if its a fueling problem causing this that would mean you're running number 4 piston leaner than lean best torque and the other pistons are going to be burning opposite of that to give an overall 10-11 a/f, drawing the conclusion that if 4 is lean, the others are very rich which is nearly as bad.

 

Sounds like what someone above said EGT probes needed in all 4 primary tubes to best determine balance of A/F ratio amongst the cylinders.


Mike

 

Also good points Witt. I wish there was a way could see how well the oil was being distributed to each cylinder. I don't think it is a coolant issue since the hot coolant exits from cylinder 1...or maybe there is poor coolant flow in that part of the block. I know that wreaks havoc on the 03-04 SVT Cobra. Or perhaps it is an issue with the oil squirters or oil flow. I really wish I knew for sure, but thus far that is the best info I have recieved on the matter from someone that races Ecotecs.

In the case of Blown 4-banger, he tuned himself for ZERO knock. He also monitored it and he claims there was no KR at the time of the failure or at all that night.

 

Yeah, I have no idea how to tell if this is an oiling problem like the local people are telling me or if it is an A/F problem.

I agree though, those that are most experienced with the engines will probably have the best solution. I've always been a fan of following what GM recommends (build book, GM parts, etc) and I myself have never had an engine problem with this car. I think instead of dropping pulley sizes to the point where you actually begin to lose horsepower rather, change out valve springs, raise the redline and put a bottle on it like they recommend if you wanna go fast.

Again, just my 2 cents.

 

Yeah the M62 is not the best power adder when you get past GM Stage 2. I think the turbo, twinscrew or even nitrous(cringe) would allow us to get a lot more power to the ground on stock internals. It's not that we will be actually making more power, but making it more efficiently. The few cars that have gone turbo are proof.

 

Head work and cams is the way to make **** tons of power. Everyone knows all the power to be made is in the top end of the motor (head/cams). That how I'm making my power, until I get the twin screw.

 

OK..Im going to try to be as non bashing as i can here but please bear with me:

I see your dealership is as smart as mine...in which case this means i have forgotten more about tuning cars then they have ever known.

First...give their mechanic with the 2.5 another 5 months with that 2.5 and hell have blower bearing problems. Easiest way to tell that i can see is yank the blower...If its all black on the inside of the intake manifold ur needle bearings have liquidized all the grease in em and they are going to ruin themselves soon...in a very nasty and noisy fashion... I have evidenced this on a few cars including my own. IMHO 2.7 is the smallest u can go without risking ur blowers bearings. Though...constant meth injection on a 2.5 should allow the bearings to survive longer due to reduced bearing temperatures.

Next on the AF dilema...I agree with witt. We had a car running particularly rich and he destroyed the bottom ring land. Other cars have been fine. Cylinder gas washdown is a real and possible issue in these cars...ESPECIALLY below 11.5afr

Link with afr data
http://www.max-boost.co.uk/max-boost...20metering.htm

In the gm build book itself it says they tune the top fuel ecotecs to rich best tq...11.5...anything less is contaminating ur oil

But here comes the best part. I have an EGT gauge on my car at cylinder #4 (like 3" from the head). When I was running afr's in the 10s and just stage 2 timing (I was tunig the turbo) I was seeing the egt in cylinder 4 go from 1400deg F to over pegging my gauge out at OVER 1600deg F in a few seconds of WOT. Now since I have a lil metalurgist experience I'll explain why this is horrific. Our head are aluminum..fact...aluminum has a alpha/beta + liquidus/eutectic temperature right around 1450 degrees...go above that and depending on the alloy it changes into liquid either faster or slower. But at 1450 is starts to change. So when the egts raise up over 1450 is doesnt take long for those temps to transfer into the head...and when its up there long enough boom instant head melt down and end of the fun for you

So running these stage 2 timings and 10s in afr produces INSANELY hi egts...which imho and which science proves is just a recipe for disaster via melted head/burnt valves.

It should be noted that once we leaned the car out and added some timing the egts went to 1400 and stayed there constantly.

What im saying in a nutshell Tune to 11.5 and run as much timing as u can get without knock. This will lower ur egts and provide more power and tq then a lower af ever will...not to mention increase engine life and reduce oil contamination

Dan

 

Reading through this thread gives me mixed emotions. Since I want to keep my warnnity, and I'm very happy with my SS/SC where it stands now. Is it safe to say GMP Stage II, on the GMP Stage II reflash, with other bolt ons such as GMP exhaust, GMP manifold, Injen CAI, and dual pass with a larger surge tank be a perfectly safe set up that will last a long time? I'm trying to go for a car that has some performance but will last if I take good care of it. I personally don't care for real small pullies on the stock blower. I would be real happy to hear some feed back on an all GMP set up such as mine. Talking about engine wear, and AFR and all of the above that has been mentioned in this thread.

 

interesting. some people still don't understand, that timing directly affects air fuel ratios.

 

I know I'm late on this but...

Has anyone just thought of NOT going with an extremely small pulley?

or even more...

Getting a more EFFICIENT compressor?

This seems more logical than richening the **** out of your engine.

I'll probably get **** for saying something that makes sense...don't really care.

 

People have thought of going for a more efficient compressor. I was screaming for a turbo kit when I had my Cobalt, and the ones that actually have went turbo should be proof that it's crossed people's minds. I think alot of people are just trying to push the stock S/C to it's limits. And now we're finding out what the limits are after people have been running their set ups for a while.

 

I think me and you and people with a bit of intelligence saw the limit MONTHS and MONTHS ago...

It's been pushed.

It has more to do with people not wanting to spend the money for the performance they want, so they are trying to find a short cut and people are afraid to try something different. It's easier to buy a pulley than to buy a new compressor and actually put some effort into something.

Fact is that people want something out of the stock supercharger setup that is going to be more difficult than they thought (or still think).

 

Agreed. Gentlemen, start your tuning......for a turbo that is.

P.S. I took a short cut to get the performance I wanted, it just wasn't a cheap one.

 

Once you switch to a more efficient compressor, whether it me turbo, twin screw, or other, you won't need nearly as much boost to make the numbers they want. More than anything, I think the extreme boost is what is causing the problems. Granted the heat issue doesn't help in the least.

As far as AFR, I noticed that link didn't specify if the motor was N/A or boosted. It makes a difference from what I have read about tuning. You want to run richer on a boosted motor.

I wonder if the fact that the top fuel cobalt uses higher octane methanol contributes to the need for it to be leaner since higher octane = more difficult to combust and longer to burn.

 

This is a great discussion with some very valid points, being a stickied thread may not be the wisest thing at this point.

 

You're talkin about Randy right? All 278 motor wheel hp, and 378 sprayed wheel hp. Did he show you his custom header? Not too shabby huh?

Just so you guys know, he has been running this combo for 4, maybe 5 months now(I'm not sure, he had this setup before i got my car), and he has been to the track countless times. Although he doesn't pound on the car on a daily basis, as I'm sure most of you guys do.

But he does know that he is pushing way too much power for the stock internals, and has new rods and pistons on the way from GMPP. I think he said he's gettin em for free too. (Drool)

ETID FTMFW!!

 

Yeah it is Randy. Iknow he was running the Intense stage 3 just before HP Tuners was released. Not sure when he swapped to the 2.5", but it has been that way for well over 6 months. I haven't seen his header yet, he was not there on Saturday. I talked with Tom the service manager.

 

while im no pro at the internal/tuning side of things like some.....

I also strongly agree that this car in stock form is limited to 300hp or less.

Not totally unlike another car similar to ours. the srt4.
while they can do a bit better on their stock hairdryer.....they really only get the big well known power of the srt4 from a bigger form of F/I

Im still waiting with bated breath for tags S/C swap, and more numbers from their turbo swap.

I think thats where the future of cobalt modding should be.

not pouring cooling mods at a completely overspun blower.